FrSky Hack Module in a 35mhz 6ex

[biggestgerbil]

Anyone done this?
I have a 35mhz Futabe 6EX and would like to fit a FrSky hack module therein.
Can anyone tell me where to connect to inside.
I have sucessfully done a couple of Challenger sets but they are quite simple.
Thanks in advance

[Mike_K]

The easiest way on most Futaba sets is to pick up the ppm on the buddy box connector. The buddy box ppm signal has proper high and low logic levels so will work with just about all modules including the FrSky hack and LemonRx. I think the 6EX has the more modern rectangular connector which are a little more tricky to connect to as they are smaller than the 1980s round DIN connector, but in the early days of 2.4GHz, I converted a few sets for clubmates.

[bluejets]

Does Futaba being inverted PPM affect the mod?

[Phil_G]

This must be the must frequent question of all
Conversions are addictive, No-one has ever had the self-control to do one solitary conversion!
Resurrecting these old sets is a really satisfying hobby in itself and ideal for cold/dark/wet evenings huddled around a blazing soldering iron.
Face it, you're going to be doing a few. So equip yourself with some test gear, it doesnt have to be expensive or complicated.
My suggestions:

A cheapy multimeter, these can be had for £5 or less. Dont bother with a posh one unless you have other uses for it.

Martins 2.4G scanner is quite superb for checking a transmitter's output. Its DIY, but just three ready-made modules linked with a few wires. If you use an RF-Nano, its just two modules linked with 4 wires, it doesn t get any simpler. It costs maybe £3-4 and 10 minutes of your time to assemble.

A PPM meter of some sort, there ara at least three for DIY described here on the forum, Martins is two modules and four wires. Mine has more facilities but is a bit more involved. Mikes is a super-duper-all-in-one.
...or...
A cheap & cheerful pocket-scope like the one pictured below.
These can be bought for as little as £15, you dont need a posh high-bandwidth scope.
Of course I have a posh scope too but this pocket scope is only 200k B/W and displays PPM perfectly, for £20.
Either the scope or PPM meter will show the PPM stream generated by your encoder and can of course be used to find a PPM source.
The pocket scope can be also used to measure voltages like a multimeter but maybe not quite so accurately.

Hope this is of interest!
Cheers
Phil

[stuart mackay]

Does Futaba being inverted PPM affect the mod?

The LemonRx DIY module https://www.ebay.co.uk/itm/133704108565 handles both pos. an neg. going ppm with no issue.

[Mike_K]

Just a quick note that the LemonRx DIY module will NOT work with a Futaba encoder without fitting a Schottky diode and pull-up resistor on the ppm input, so it is an easy fix, but it is one of the minor criticisms of the LemonRx module. Why oh why didn't they copy FrSky, the 4-in-1 modules and OrangeRx which use a schottky diode and the microprocessors internal pull-up for the ppm input. That way they would work with Futaba and JR type encoders and the modern Arduino based encoders. I guess it was so the ppm signal can go negative relative to ground without damaging the module?

The LemonRx modules expect a full-swing logic level ie a ground and a positive voltage ppm signal to work, it uses a high impedance resistor in the ppm input, but no pull-up resistor (like FrSky, OrangeRx etc). The Futaba encoders ppm output is open collector, they pull down to ground and then float/open circuit for the "positive" part of the ppm pulse. With a schottky diode and pull up resistor, you then have the full-swing logic level and it will work.

Edit

I meant to add that if you use the buddy box trainer port, the LemonRx module will work without the Schottky diode and pull up resistor as the port has normal logic levels.

Most modern modules used for conversion will work with both "positive and negative" logic polarities, certainly the LemonRx, FrSky, 4-in-1 multi-modules, OrangeRx etc. In the early days it was common to de-case a Spektrum DM8 or DM9 or Futaba TM7 module and they required the correct ppm polarity